This paper studies different techniques for measuring and decreasing inconsistency of a knowledge base. We define an operation that allows to decrease inconsistency of a knowledge base while losing a minimal amount of information. We also propose two different ways to compare knowledge bases. The first is a partial order that we define on the set of knowledge bases. We study this relation and identify its link with a particular class of inconsistency measures. We also study the links between the partial order we introduce and information measures. The second way we propose to compare knowledge bases is to define a class of metrics that give us a distance between knowledge bases. They are based on symmetric set difference of models of pairs of formulae from the two sets in question.